The present invention relates to a scroll fluid machine suitable for use in an air compressor, a vacuum pump, etc.
A generally known scroll fluid machine has a casing and a fixed scroll member provided in the casing. The fixed scroll member has a spiral wrap portion standing on an end plate. A driving shaft is rotatably provided in the casing. An orbiting scroll member is orbitably provided on the distal end of the driving shaft in the casing. The orbiting scroll member has a spiral wrap portion standing on an end plate so as to overlap the wrap portion of the fixed scroll member to define a plurality of compression chambers.
In this type of known scroll fluid machine, the driving shaft is externally driven to rotate, causing the orbiting scroll member to perform an orbiting motion with a predetermined eccentricity with respect to the fixed scroll member, thereby sucking a fluid, e.g. air, from a suction opening provided at the outer periphery of the fixed scroll member, and successively compressing the fluid in the compression chambers formed between the wrap portions of the fixed and orbiting scroll members. Finally, the compressed fluid is discharged to the outside from a discharge opening provided in the center of the fixed scroll member.
In another known scroll fluid machine, a lubrication pump is provided between the casing and the outer periphery of the end plate of the orbiting scroll member. The lubrication pump operates in response to the orbiting motion of the orbiting scroll member to lubricate the driving shaft, the orbiting scroll member, etc. That is, a lubricant contained in the casing is led to the area between the casing and the outer periphery of the end plate of the orbiting scroll member by the lubrication pump and thus supplied to the driving shaft, the orbiting scroll member, etc.
Incidentally, in the above-described known scroll fluid machine, the lubrication pump is provided between the inner periphery of the casing and the outer periphery of the end plate of the orbiting scroll member. Consequently, the lubrication pump is placed near the sliding contact surfaces of the orbiting and fixed scroll members, and it is likely that the lubricant pressurized by the lubrication pump will enter the area between the sliding contact surfaces of the orbiting and fixed scroll members.
Therefore, the prior art involves the danger that the high-pressure lubricant, which has been pressurized in the pump chamber of the lubrication pump, may enter the area between the sliding contact surfaces of the fixed and orbiting scroll members and leak into the compression chambers. If the lubricant leaks into the compression chambers, it is difficult to discharge a clean compressed fluid to the outside. Thus, if there is likelihood that the lubricant may leak, the apparatus cannot be improved in performance and reliability.
In view of the above-described problems with the prior art, an object of the present invention is to provide a scroll fluid machine designed to be capable of preventing the entry of the lubricant from the lubrication pump into the compression chambers and of discharging a clean compressed fluid at all times and also capable of efficiently lubricating the driving shaft, etc. and hence improving the apparatus in performance, reliability and so forth.